منابع مشابه
Coexistence of Qubit Effects
We characterize all coexistent pairs of qubit effects. This gives an exhaustive description of all pairs of events allowed, in principle, to occur in a single qubit measurement. The characterization consists of three disjoint conditions which are easy to check for a given pair of effects. Known special cases are shown to follow from our general characterization theorem.
متن کاملCoexistence of qubit effects
Two quantum events, represented by positive operators (effects), are coexistent if they can occur as possible outcomes in a single measurement scheme. Equivalently, the corresponding effects are coexistent if and only if they are contained in the ranges of a single (joint) observable. Here we give a necessary and sufficient condition for the coexistence of a pair of qubit effects.
متن کاملCoexistence of Quantum Effects
The witness set W(A, B) for two quantum effects A, B is the set of effects that verify the coexistence of A and B. We first study the properties of W(A, B). We then introduce a measure of sharpness Sn(A) for an n-dimensional quantum effect A. We show that S2(A) has natural properties that a measure of sharpness should possess and conjecture that Sn(A) also has these properties for n > 2. Finall...
متن کاملThe witness set of coexistence of quantum effects and its preservers
One of unsolved problems in quantum measurement theory is to characterize coexistence of quantum effects. In this paper, applying positive operator matrix theory, we give a mathematical characterization of the witness set of coexistence of quantum effects and obtain a series of properties of coexistence. We also devote to characterizing bijective morphisms on quantum effects leaving the witness...
متن کاملDecoherence effects on quantum Fisher information of multi-qubit W states
Quantum fisher information of a parameter characterizing the sensitivity of a state with respect to parameter changes. In this paper, we study the quantum fisher information of the W state for four, five, six and seven particles in decoherence channels, such as amplitude damping, phase damping and depolarizing channel. Using Krauss operators for decoherence channels components, we investigate t...
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ژورنال
عنوان ژورنال: Quantum Information Processing
سال: 2009
ISSN: 1570-0755,1573-1332
DOI: 10.1007/s11128-009-0109-x